Vulnerability in Linux kernel (CVE-2025-21720)
Summary
Vulnerability in Linux kernel (CVE-2025-21720). Risk of unauthorized operations or information disclosure.
Original description
The description as published by the source.
In the Linux kernel, the following vulnerability has been resolved:
xfrm: delete intermediate secpath entry in packet offload mode
Packets handled by hardware have added secpath as a way to inform XFRM
core code that this path was already handled. That secpath is not needed
at all after policy is checked and it is removed later in the stack.
However, in the case of IP forwarding is enabled (/proc/sys/net/ipv4/ip_forward),
that secpath is not removed and packets which already were handled are reentered
to the driver TX path with xfrm_offload set.
The following kernel panic is observed in mlx5 in such case:
mlx5_core 0000:04:00.0 enp4s0f0np0: Link up
mlx5_core 0000:04:00.1 enp4s0f1np1: Link up
Initializing XFRM netlink socket
IPsec XFRM device driver
BUG: kernel NULL pointer dereference, address: 0000000000000000
#PF: supervisor instruction fetch in kernel mode
#PF: error_code(0x0010) - not-present page
PGD 0 P4D 0
Oops: Oops: 0010 [#1] PREEMPT SMP
CPU: 0 UID: 0 PID: 0 Comm: swapper/0 Not tainted 6.13.0-rc1-alex #3
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.13.0-1ubuntu1.1 04/01/2014
RIP: 0010:0x0
Code: Unable to access opcode bytes at 0xffffffffffffffd6.
RSP: 0018:ffffb87380003800 EFLAGS: 00010206
RAX: ffff8df004e02600 RBX: ffffb873800038d8 RCX: 00000000ffff98cf
RDX: ffff8df00733e108 RSI: ffff8df00521fb80 RDI: ffff8df001661f00
RBP: ffffb87380003850 R08: ffff8df013980000 R09: 0000000000000010
R10: 0000000000000002 R11: 0000000000000002 R12…
Source: NIST National Vulnerability Database NVD
Auto-generated summary
Assembled by SecPulse from the source data (CVSS, CWE, affected versions) using templates — no AI involved. Check the original description and references below for exact details.
A vulnerability tracked as CVE-2025-21720 has been found in Linux kernel.
Risk of unauthorized operations or information disclosure. CVSS score: 7.5/10.
What to do: apply the vendor's official patched release.
If unsure, ask your IT team or search "Linux kernel CVE-2025-21720" on the vendor's site.
CVE-2025-21720 (Linux kernel) — CWE-476 / CVSS v3 7.5
Attack vector: remote (network-reachable) / unauthenticated / no user interaction
Plan: 1) Audit SBOM/dependencies, 2) Stage→prod upgrade, 3) Add WAF/proxy monitoring on affected endpoints, 4) Hunt IOCs in logs.
Refs: see the GHSA / vendor advisory / patched release linked on this page.
A vulnerability (CWE-476) exists in Linux kernel.
Check the vendor advisory for the affected versions of Linux kernel.
Severity: High (CVSS 7.5/10). Risk of unauthorized operations or information disclosure.
Update to the patched release per vendor advisory.
Until the patch is applied: disable the affected feature, apply WAF rules, or restrict access via network ACLs.
Search webserver/proxy logs for unusual request patterns matching this CVE's known IOCs. Audit SBOM/dependencies to find affected services.
Response actions
Concrete steps and command examples for SOC/SRE teams to execute in order
-
1Identify exposure identify
Audit SBOM/dependencies for affected components.資産台帳・SBOM・依存マニフェストで Linux kernel を使っているサービスとバージョンを洗い出す。
-
2Post-deployment verification verify
Confirm patched version is live in productionパッチ適用後、ステージングで PoC または同等の悪用パターンを再現して脆弱性が閉じたことを確認。本番ではアクセスログ・WAF でアラート再発が無いか継続監視。
Affected packages
Fix status by distribution
Fixed packages published by each distribution for this CVE
- BellSoft Alpaquita BELL-CVE-2025-21720 linux-lts Fixed in: 6.12.41-r0
- Debian DEBIAN-CVE-2025-21720 linux Fixed in: 6.12.13-1
- Ubuntu UBUNTU-CVE-2025-21720 linux-hwe-edge
References
- advisory github.com
- advisory nvd.nist.gov
- package git.kernel.org
- web git.kernel.org
- web git.kernel.org
- web git.kernel.org
- web git.kernel.org